In practice, road finishing machines are employed to install new road surfaces by means of a screed arranged thereon. The laying material required for this is supplied from a material bunker of the road finishing machine which is arranged at the front of the road finishing machine as viewed in the direction of laying. Via material transporting means, the laying material is transported from the material bunker underneath the control platform rearwards to the screed, spread in front of the latter by means of a spreading screw, and finally installed under the screed by means of heated compacting units to form the new pavement.
To be able to install an even pavement on the ground on which the road finishing machine is moving, the screed is mounted to the chassis of the road finishing machine by means of height-adjustable screed arms. The leveling of the screed may be performed by means of a controlling system of the road finishing machine. Here, the leveling of the screed depends on the surface condition of the ground or the desired thickness of the road surface to be installed.
It is well-known that for leveling a screed of a road finishing machine, an elongated rigid measuring beam is laterally mounted to the road finishing machine and positions a plurality of sensors on one side over the ground on which the road finishing machine is moving, and on the other side over the new installed paving layer behind the screed. A problem of the known measuring beam retainers is that their assembly is difficult and time-consuming, and in particular the attachment to the road finishing machine requires good skills and in most cases several persons.
DE 602 26 237 T2, for example, shows a measuring beam device with beams arranged one upon the other which are horizontally telescopically extendable along the road finishing machine to position sensors for height measurement to control a leveling system of the road finishing machine laterally of the road finishing machine over the ground. The respective telescopic beam segments may be fixed at a desired point by means of anchors provided thereon. It is here a disadvantage that the telescopic measuring beams altogether have a high weight and can therefore be oriented horizontally only with high expenditure of force to position the respective leveling sensors at a desired point above the ground. Furthermore, the telescopic measuring beam construction is expensive to manufacture.
U.S. Pat. No. 5,975,473 discloses a measuring beam device laterally mounted to the road finishing machine. The measuring beam device is mounted to a screed arm of the road finishing machine via articulated swivel arms. Furthermore, the measuring beam device comprises a measuring beam laterally supported along the road finishing machine with a central beam and extension beams mounted to the ends thereof. At least for positioning the leveling sensors mounted to the central beam, however, essentially the complete measuring beam device has to be moved which renders the positioning of the sensors above the ground difficult.
DE 691 26 017 T2 discloses a road finishing machine with a measuring beam fixed to it which positions leveling sensors only at predetermined points above the ground. A displacement of the leveling sensors seems not to be possible there, so the measuring beam cannot be employed at different road finishing machine models.
The subsequently published European patent application No. 16 164 466.1 by Joseph Vögele AG describes a retainer device for supporting and positioning at least one sensor unit which may be mounted to an assembly beam by means of a claw-like retainer. To position the sensor unit along the assembly beam, the claw-like retainer is released from its clamping attachment and laterally displaced to a desired point along the assembly beam. The displacement of the retainer along the assembly beam is easily possible, where in particular the dislocation of the assembly beam from one side of the road finishing machine to the other side requires additional assembly works to correspondingly mount the retainer to the assembly beam.